This invention relates generally to scatterometer analysis and more particularly to a scatterometer method that provides a practical means for analysis of a sample which eliminates the requirement of rotating, tilting or otherwise moving the sample during the course of a scatterometer measurement.
Scatterometer arrangements, like those described in the prior art patents and patent application cited above, have been used for characterizing the microstructure of microelectronic and optoelectronic semiconductor materials, computer hard disks, optical disks, finely polished optical components, and other materials having lateral dimensions in the range of tens of microns to less than one-tenth- micron.
Exemplary of the prior art are three publications. The first is by Michael R. Murnane, et.al., "Developed Photoresist Metrology Using Scatterometry", Proceedings of the SPIE, Integrated Circuit Metrology, Inspection, and Process Control VIII, Vol 2196, pp 47-59 (1994); the second is by Michael R. Murnane, et. al., "Scatterometry for 0.24 .mu.m-0.70 .mu.m Developed Photoresist Metrology", Proceedings of the SPIE, Integrated Circuit Metrology, Inspection, and Process Control IX, Vol 2439, pp 427-436 (1995); the third is by Christopher J. Raymond, et. al., "Metrology of Subwavelength Photoresist Gratings Using Optical Scatterometry", Journal of Vacuum Science and Technology, B, Vol 13(4), July/August, pp 1484-1495 (1995). This referenced prior art extends the capability of the scatterometer measurements to enable characterization of structure having lateral dimensions that are sub-micron. The prior art scatterometer arrangement discussed in the literature is disadvantageous in that it requires rotation of the sample while performing a scatterometer measurement. This requirement precludes their use in applications in which the sample must remain stationary. In addition, the rotation stages employed in this prior art scatterometer represents a mechanical complexity, which can result in undesirable optical and mechanical misalignment. Finally, the sample rotation required in this prior art scatterometer necessitates increased sample handling, thus increasing the risk of damage to the sample.
It is therefore the principle object of the present invention to provide a scatterometer method that provides a practical means of sample analysis, This is accomplished by illuminating the sample with light that has a broad spectral composition, characterizing the spectral composition of the light that is diffracted from the sample, and analysis of the diffracted light using techniques that are based upon multivariate statistical techniques and theoretical techniques; collectively the elements of this method eliminates the requirement to rotate or otherwise move the sample.